Adjustable beam-trace-positioning amplifier



y 28, 1953 M. MARON 2,647,174

ADJUSTABLE BEAM-TRAGE-POSITIONING AMPLIFIER Filed Sept. 23, 1950 43 4 UNgIALANCED BALANCED emu. AMPLIFIER SOURCE SIGNAL SOURCE zzvmvrox I MEYER MA RON A T TORNEYS Patented July 28, 1953 ADJUSTABLE BEAM- TRACE-PO SITIONING AlVIPLIFIER Meyer Maron, Passaic, N. J assignor to Allen B.

Du Mont Laboratories, Inc., Clifton, N. J., a corporation of Delaware Application September 23, 1950, Serial No. 186,474

2 Claims. (01. 179-171) 1 The present invention is concerned with improvements in circuits for positioning cathode ray beams as used for example in cathode ray oscillographs.

2 186,478 of Peter S. Christaldi now Patent 2,631,200 issued March 10, 1953, entitled Gain Control Circuits filed concurrently herewith and assigned to the same assignee as the present ap- Cathode ray oscillographs customarily use di- 5 plication. Also connected to these cathodes is rect current amplifiers in order to be able to a balancing circuit comprising a variable resistor indicate direct current and low frequency alter- I8 connected between the cathode of tube I2 nating current signals. Balanced amplifier stages and ground and a pair of fixed resistors I9 and are generally utilized because of their well known ZI connected between the cathode of tube I3. advantages in direct current amplification. How- 10 and grou d- This balancing 00 110 circu t is ever, in such circuits it becomes important to be able to adjust the zero-signal beam trace position, both for centering the indication on the cathode ray screen and for being able to select a given portion of the indication for exami- 15 plicatioh- The grid o u I3 is ect y nation where desired. grounded at r The present invention provides improved read- The Variable tap 22 0f the gain control 11y usable beam posj tj oning means for these p'urtentiometer I! is connected directly to the con-: poses. According to the present invention b trol electrode of tube 23 which together with positioning is provided by control of the bias of tube 24 forms the following balanced amplifier one tube of a balanced amplifier over a relatively Stage- The anodes of tubes 23 and 24 are wide range, thereby permitting wide range connected through respective load resistors 25, 28 trol of the beam position to a source I6a of positive potential whose nega- Other objects and advantages of the present five terminal is also srounded- Source fia may invention will become apparent from considering be the Same Source as 16 Where desired-r The the following description of a preferred embodicathodes of tubes 23 and 24 are connected-17" ment thereof, taken in conjunction with the apgether and through a common cathode biasing pended drawing which in its Single figure Shows resistor 21 to ground at 28. Resistor 21 is bya schematic wiring diagram partially in block Passed by condenser o supply the signal form of a cathode ray oscillograph circuit 30 voltage to the control electrode to tube 24, this r oratjng the present invention control electrode is connected through a cur- In rectangle as lBSlSlSOl t0 an unbalanced signal source represents any suitof a potentiometer one terminal of which able source of unbalanced signal which it is is connected to the junction of resistors I9 and sired to amplif before application to the de- 35 It will be apparent that when a signal is fl tin means of a cathode ray tube By way applied to the control electrode of tube I2, it proof example, this unbalanced signal source II duces Corresponding Variations in the potenmay represent directly a generator of Such tial of the cathode of that same tube. This signals or it may represent unbalanced input nal is supplied through potentiometer I1 to the minals for the oscillograph' 40 cathode of tube I3, whose control grid is ground- The unbalanced signal output from source II eby pp y a fl r g al Of 01)- is applied to the control electrode of tube I2 of P051156 p a ity to the inpu C rcu t of tube l3. a first amplifier stage formed by tubes I2, I3. A portion of this Signal W h ppe rs between Tubes I2 and I3, while illustrated as in the form the cathode of tube t and round is taken ofi of triodes, may be any suitable amplifying tubes, at ju n 34 a d upp d to th ontr l rid of such as of the tetrode, pentode, screen grid or tube 4 ro a Portion of p eter 33 other type. The anodes of tubes I2 and I3 are and the O connected through a common resistor It to a Because Of the 1055 Of low frequency source I6 of positive potential. It will be underpo of the Signal appearing at the cathode stood that the negative terminal of the source f e l f r s pl ion o the control I6 is connected to ground. electrode of tube 24, a capacitative voltage divider The cathodes of tubes I2 and I3 are connected formed by condensers 36 and 31 is connected beto the outer terminals of a potentiometer I1 servtween the cathode of tube I3 and ground. The mg as a gain control in the manner described junction of these condensers 36 and 31 is then and claimed in copending application Serial No. 56 connected through resistor 31 to the control grid described and claimed in my copending application Serial No. 186,473, entitled D. C. Balance- Adjustment filed concurrently herewith andassigned to the same assignee as the presentapof tube 24 to equalize the loss of high and low frequency components. In addition, the tubes 12 and I3 are supplied with a common plate resistor 14 similarly producing improvement in equalization. The resistor I4 is chosen of proper value to produce a signal at the cathode of tube I3 substantially equal in amplitude and opposite in phase to the signal otherwise present at that point, thus resulting in cancellation. This assures better high frequency response at the low end of the amplitude control ll.

To provide the control electrode" of tube 24 with adjustable bias, the other terminal of potentiometer 33 is connected through a suitable fixed resistor 38 to a source 161) ofpositive potential whose negative terminal is also grounded. Source 16b may be the same as either or both sources [6 and 16a. It will be understood that the control of the bias of tube 24 by positioning control 33 serves to correspondingly control the plate current of tube 24 alone without afiecting that of tube 23. This correspondingly alters the volt drop in resistor 2-6 and provides an unbalance in the output derived from the two anodes of tubes 23 and 24. This output is fed through a balanced amplifier 4| of any desired type to one pair of defleeting means of the cathode ray tube 42. In this instance, these deflecting means are illustrated as deflecting plates and the output of amplifier 4| is supplied to the horizontal plates 43. The vertical deflecting means, in the form of plates 44, are supplied by any suitable desired signal, as from a source 45.

The position control 33 has a relatively wide range of variation of bias on the control electrode of tube 24. In one system designed, this permits any portion of the pattern to be posi tioned on the screen, even with an expansion of six times the full screen diameter. This makes an instrument having a 5-inch tube equivalent to a 30 inch tube having a movable 5-inch mask which permits any 5-inch portion of the trace to be examined.

While the present invention has been illustrated with respect to a preferred embodiment thereof, it is to be understood that the foregoing description is illustrative only and is not to be 4'. taken in a limiting sense, the invention being defined solely by the appended claims.

What is claimed is:

1. An adjustable beam-trace-positioning amplifier for cathode ray oscillographs or the like, comprising a pair of electron tubes, an input circuit for one of said tubes adapted to have a signal applied thereto, means coupling the cathode of said one tube to the cathode of the other of said tubes to transfer said input signal to said other tube, the control electrode of said other tube being grounded, resistance means between each of said cathodes and ground, a second pair of electron tubes, the input electrode of one of said second tube pair being coupled to the cathode of said one tube of said first tube pair, a source of positive voltage, means coupling said source to the resistance means between the cathode of said other tube of said first tube pair and ground, said latter coupling means including a potentiometer and means coupling the variable tap of said potentiometer to the control electrode of the other tube of said second tube pair to adjustably control the bias thereof.

2. An amplifier as in claim 1 further including a pair of series-connected condensers connected between ground and the cathode of the other tube of said first tube pair, the junction of said condensers being coupled to the control electrode of the other tube of said second tube pair for frequency equalization.

MEYER MARON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,208,254 Geohegan July 16, 1940 2,240,635 Avins May 6, 1941 2,310,342 Artzt Feb. 9, 1943 2,329,073 Mitchell et a1. Sept. 7, 1943 2,471,449 Reade et al May 31, 1949 2,529A59 Pourciau et a1. Nov. 7, 1950 FOREIGN PATENTS Number Country Date 584,191 Great Britain Jan. 9, 1947 

